<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>下拉菜单-DropDownDemo</title>
    <link rel="stylesheet" href="../css/bootstrap.min.css">
</head>
<body>

    <div class="container">
        <div class="dropdown">
            <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
                下拉菜单
                <span class="caret"></span>
            </button>
            <ul class="dropdown-menu" role="menu">
                <li class="dropdown-header">大写</li>
                <li><a href="#" role="menuitem">一</a></li>
                <li><a href="#" role="menuitem">二</a></li>
                <li><a href="#" role="menuitem">三</a></li>
                <li><a href="#" role="menuitem">四</a></li>
                <!--<li class="dropdown-header">小写</li>-->
                <li class="divider"></li>
                <li><a href="#" role="menuitem">1</a></li>
                <li><a href="#" role="menuitem">2</a></li>
                <li><a href="#" role="menuitem">3</a></li>
                <li><a href="#" role="menuitem">4</a></li>
            </ul>
        </div>
    </div>

<script src="../js/jquery-3.3.1.js"></script>
<script src="../js/bootstrap.min.js"></script>
</body>
</html>